Pregnancy-specific-beta 1-glycoprotein: effect on lymphocyte proliferation in vitro.

The effects of three different preparations of pregnancy-specific-beta 1-glycoprotein (SP1) were investigated in parallel with progesterone, oestradiol and human chorionic gonadotrophin (hCG) on the proliferative response of lymphocytes in the mixed lymphocyte reaction (MLR), and to the mitogens phytohaemagglutinin (PHA) and pokeweed mitogen (PWM). A dose-related inhibition of the MLR was obtained with SP1 at 2.5-10 mg/l. SP1 also inhibited the PHA response at 10 mg/l, but had no effect on the PWM response at these concentrations. Progesterone and oestradiol inhibited all systems at 10-20 mg/l while hCG inhibited all systems at 1500-3000 IU/ml. The observations suggest that SP1 selectively inhibits the proliferative responses of T lymphocytes at the concentrations studied.